NACL (Network Access Control List)

NACL and the security group both act as a firewall. NACL is used on the Subnet level and Security Group on the instance level.

Ø  NACL allows or denies (Stateless) specific inbound or outbound traffic at the subnet level. You can use the default network ACL for your VPC, or you can create a custom network ACL for your VPC with rules similar to the rules for your security groups to add an additional layer of security to your VPC.

 

Ø  Each subnet in your VPC must be associated with a network ACL. You can associate a network ACL with multiple subnets. However, a subnet can be associated with only one network ACL at a time. The previous association is removed when you associate a network ACL with a subnet.

 

Ø  A network ACL has inbound rules and outbound rules. Each rule can either allow or deny traffic. Each rule has a number from 1 to 32766. evaluate the network ACL rules when traffic enters and leaves the subnet. Rules are evaluated starting with the lowest numbered rule.

 

Ø  NACLs are stateless, which means that information about previously sent or received traffic is not saved. Security groups are stateful, which means that information about previously sent or received traffic is saved. In Stateless inbound and outbound both rules should be defined and in stateful inbound rule defined and automatically outbound rule defined.

 

 



 

 

NACL (Network Access Control List) LAB

1.    Create VPC-1

2.    Create a Subnet for VPC-1

3.    Create IGW for VPC-1

4.    Attach IGW with VPC-1

5.    Define the Route Table for VPC-1 and add the Rule for IGW.

6.    Associate subnet with VPC-1

7.    Create Network ACL

8.    Associate Subnet with Network ACL.

9.    Define inbound (RDP, All Traffic) and outbound (HTTP/HTTPS) rules on NACL.

10.           Create EC2 Instance for VPC-1 and enable public IP

11.           Now we can access the EC2 Instance but it will not respond due to we didn’t define an outbound rule for response. So, we will allow All Traffic (1024-65535) in NACL.

12.           Now again Access EC2 through RDP.it will response.

 

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